Method for Transmitting High-Priority Packets in an IP Transmission Network

1. A method performed by a packet transmitter for transmitting high priority packets in an Internet Protocol (IP) based transmission network wherein low-priority packets or fragments of packets are transmitted between a transmitter and a receiver and wherein high priority packets pre-empt low-priority packets, the method comprising the steps, performed by the transmitter, of: determining whether a low-priority packet or a fragment of a low-priority packet is being transmitted from the transmitter to the receiver when a high-priority packet requires transmission; activating a reserved bit within the IP header of the high-priority packet, as a pre-emption indicator, and suspending transmission of said low-priority packet or fragment of a low-priority packet, in the event that a low-priority packet or a fragment of a low-priority packet is being transmitted; transmitting the high-priority packet having the pre-emption indicator activated; and restarting the transmission of the low-priority packet or the fragment of the low-priority packet after having transmitted the high-priority packet, wherein the reserved bit is within the IP header as a packet start indicator in each low-priority packet or fragment, wherein the reserved bit used as a packet start indicator is set to a first binary value in a first segment of a low-priority packet or fragment being transmitted, the reserved bit being reset to a second binary value when a high-priority packet requires transmission and a low-priority packet or fragment is pre-empted, and wherein the reserved bit is within the flag field within the IP header of a packet.

2. The method of claim 1 , wherein the pre-emption indicator is not activated in the event that no low-priority packet or fragment is being transmitted when the high-priority packet is transmitted.

3. The method of claim 1 further comprising the step of transmitting a sweep packet when no high-priority packet requires transmission after a low-priority packet or fragment has been transmitted, the sweep packet being a packet without data indicating that the previous transmission of a low-priority packet or fragment has been completed.

4. A method performed by a receiver that receives high priority packets from an Internet Protocol (IP) based transmission network, wherein low-priority packets or fragments of packets are transmitted between a transmitter and the receiver, wherein high priority packets pre-empt low-priority packets and wherein each of the packets includes an header that includes at least a Flags field and a Type-of-Service field that is different from said Flags field, the method comprising the steps, performed by the receiver, of: determining whether a high-priority packet has been received by the receiver; determining whether a reserved bit within the IP header of the high-priority packet has been activated, the reserved bit being a bit within said Flags field within the IP header of the packet; waiting for reception of a new packet if the reserved bit has been activated, the activated reserve bit indicating that the high-priority packet has pre-empted a low-priority packet; and determining whether the reserved bit used as a packet start indicator has been activated when the packet being received by the receiver is a low-priority packet or fragment, the low-priority packet or fragment being a segment to be appended to the received low-priority packet or fragment if the packet start indicator is inactive.

5. The method according to claim 4 , wherein a previously received low-priority packet or fragment is delivered to the upper layer when the reserved bit used as a pre-emption indicator has been activated in the high-priority packet, and wherein an inactivated pre-emption indicator indicates that the transmission of the previously received low-priority packet or fragment has been completed.

6. The method of claim 5 , wherein the received low-priority packet or fragment is delivered to the upper layer when the reserved bit used as a packet start indicator is active, indicating that the reception of the previously received low-priority packet or fragment has been completed.

7. The method of claim 6 , further comprising the step of determining whether the packet being received is a sweep packet without data, the sweep packet indicating that the transmission of a low-priority packet or fragment has been completed.

8. The method of claim 7 , wherein the step of determining whether the packet being received is a low-priority packet or a high-priority packet is determined by said Type-of-Service field within the IP header of the received packet.

9. The method of claim 8 , wherein the high-priority packet is a voice packet and the low-priority packet or fragment is a data packet or fragment.